Communications　with　link　distance　of　hundreds　of　meters　and　data　rate　of　tens　of　Mbps　are　highly　demanded　in　underwater　wireless　optical　communications　(UWOC)　between　autonomous　underwater　vehicles　(AUVs)　and　submarines,　or　among　others　underwater　platforms.　In　these　cases,　a　high-power　light　source　has　to　be　used　and　an　external　modulation　must　be　imposed.　Here　we　present　an　UWOC　system　based　on　acousto-optic　modulator　(AOM),　Non-Return-to-Zero　On-Off　Keying　(NRZ-OOK)　modulation　and　520　nm　green　laser　diode　light　source.　A　data　rate　of　15　Mbps,　the　highest　reported　values　of　an　UWOC　system　using　AOM　to　our　best　knowledge,　with　9　m　distance　and　1.53　x　10(-4)　bit　error　rate　(BER),　as　well　as　the　longest　distance　of　18　m　with　12　Mbps　data　rate　and　4.7　x　10(-3)　BER　are　obtained　in　the　tap　water,　in　which　an　attenuation　coefficient　of　0.0503　m(-1)　for　520　nm　wavelength　is　measured.　By　adding　different　dosages　of　Maalox　suspension,　different　types　of　water　quality　are　prepared,　and　the　influences　of　Maalox　concentration　on　the　attenuation　coefficient　and　the　BER　are　investigated.　It　is　found　that　increasing　Maalox　concentrations　would　worse　the　scatter　effect　of　light　beam,　which　further　affect　the　transmission　performance　of　the　signal.